The proposed research is directed toward producing a small to medium diameter vascular prosthesis. Work to date has indicated that the candidate material containing the best combination of physical and biomedical properties will be thermoplastic elastomer substrate with a hydrophilic surface coating. Substrate materials being investigated are polyurethane block copolymers and saturated olefin copolymers. Various hydrogel systems including heparin containing hydrogels, will be grafted by gamma irradiation techniques to preformed vessels. Chemical methods of grafting are also being explored. Detailed studies of the grafting process and the mechanical properties of the grafted product will be conducted. The materials will be evaluated as small vessel grafts by stringent in-vivo testing in canine juglar veins and cartoid arteries by James Whiffen, Department of Surgery, University of Wisconsin.